The Data Management and Biostatistical Core (DMB) will serve several functions in the CRC/GAD. The most fundamental are data management, statistical consultation and statistical training. The Core will provide uniform data management including unified data forms, standardized coding of variables and accommodation for missing values, and will supervise data entry. The Core database will be created and managed by the Core staff through networking system which will facilitate collaboration among researchers and with the Core staff. A security system for the Core database to preserve confidentiality of patients and subjects will be established under the UNIX environment. DMB staff will work with investigators beginning from planning through implementation and analysis phase of research projects to ensure sound statistical analysis. Under the guidance of the Director of the Core, the researchers will be encouraged to conduct preliminary data analyses themselves. Formal analyses will be conducted by the Core staff, which will also suggest alternative methods for data analysis as well as assistance in the interpretation of results. Data management training and statistical training will be offered to all Center participants. The course topics will include introduction to the UNIX system, use of database software, applied statistical analysis with emphasis on longitudinal data analysis. All instructions will be accompanied by demonstration with statistical software packages.